At present, transmission networks and their interconnection in wide area synchronous grids ensure the supply with electricity over large areas. With an increasing volatility of the power supply grid, the demand for decentralized energy storage systems to solve local tasks in the power supply grid is also increasing, for example, local utilization of locally generated energy or the improvement of local electricity supplies from renewable energies along a timely prediction. Especially decentralized energy generation, for example, by means of a plurality of wind turbines and solar power stations that are distributed over areas, increasingly results in voltage shifts in the power supply grids that are difficult to control. Since only a part of the power supply grids have sufficient transport capacity, temporary local electricity surpluses and demands for electricity can no longer be transported by the power supply grid. It is therefore desirable to have decentralized energy storage systems that can be integrated into the existing power supply grids in a flexible manner depending on the particular demand, in order to improve the grid quality and security of energy supplies and to ensure electricity transport capabilities.
Due to the extension of the power supply grid, bottlenecks in the transport of electricity can be eliminated over the long term. However, an extension covering a large area is cost-intensive and requires long approval and construction phases. The support of a uniform distribution of electricity, however, requires storage solutions that can be immediately used at any location in a variable manner and quickly moved to other locations if necessary but, nevertheless, have an energy storage capacity and output high enough for grid stabilization.
Pumped storage power stations are energy storage systems that, although their capacity allows them to store large amounts of energy and be available as a minute reserve for power supply grids, are still geographically bound to their location and cannot be set up at any place and transferred when necessary. That is why these energy storage systems do not solve the electricity distribution problem because the energy of the pumped storage power stations must, if necessary, even be transported over very long distances and via power lines possibly having not enough capacity. Moreover, the erection of a pumped storage power station is complex, time-consuming and cost-intensive. Moreover, pumped storage power stations are designed for full-load operation and are therefore not adapted to improve the grid quality in small local power supply systems.
Battery storage devices represent an energy storage type that can, in some cases, be moved to other locations and therefore be used in a variable manner. Battery storage devices, however, are not adapted to be resistant to load changes during operation and quickly degrade because of temperature effects, system failures and operating errors. What is more, battery storage devices require highly intensive maintenance. Due to their high fire and chemical risks, battery storage devices additionally present an environmental and water hazard and are highly complex in terms of protection and security. Today's mechanical energy storage systems having a high capacity, such as flywheel energy storage systems, are presently set up in a stationary manner for mechanical reasons and only solve local grid problems. To date, such systems have not been mobile and can, therefore, neither be subsequently modified quickly in their capacity.